Biologically enhanced electrically-active magnetic nanoparticles for concentration, separation, and detection applications

Abstract

The disclosure generally relates to a particulate composition formed from a conductive polymer (e.g., conductive polyanilines, polypyrroles, polythiophenes) bound to magnetic nanoparticles (e.g., Fe(II)- and/or Fe(III)-based magnetic metal oxides). The particulate composition can be formed into a biologically enhanced, electrically active magnetic (BEAM) nanoparticle composition by further including a binding pair member (e.g., an antibody) bound to the conductive polymer of the particulate composition. Methods and kits employing the particulate composition and the BEAM nanoparticle composition also are disclosed.

What is claimed is: 
     
       1. A method of detecting the presence of a target analyte in a sample, the method comprising:
 (a) providing a biologically enhanced, electrically active magnetic (BEAM) nanoparticle composition comprising (i) a particulate composition comprising: a conductive polymer bound to magnetic nanoparticles, and (ii) a binding pair member bound to the conductive polymer of the particulate composition, wherein the binding pair member is complementary to the target analyte, the particulate composition ranges in size from about 1 nm to about 500 nm, and the weight ratio of conductive polymer to magnetic nanoparticles in the particulate composition ranges from about 0.1 to about 1; 
 (b) contacting the BEAM nanoparticle composition with the sample for a time sufficient to bind any target analyte in the sample to the binding pair member of the BEAM nanoparticles, thereby forming an analyte-nanoparticle complex; 
 (c) applying a magnetic field to the sample and removing a portion of the sample that is substantially free from the analyte-nanoparticle complex, thereby forming a sample concentrate that contains substantially all of the analyte-nanoparticle complex; and, 
 (d) determining the presence of the target analyte in the sample by detecting the analyte-nanoparticle complex in the sample concentrate. 
 
     
     
       2. The method of  claim 1 , wherein detecting the analyte-nanoparticle complex in step (d) further comprises:
 (d1) contacting the sample concentrate with a detection label for a time sufficient to bind the detection label to the analyte-nanoparticle complex, thereby forming a label-analyte-nanoparticle complex, wherein either (i) the detection label is complementary to the target analyte and the detection label binds to the target analyte bound to the analyte-nanoparticle complex or (ii) the detection label is complementary to the binding pair member and the detection label binds to a free binding pair member of the analyte-nanoparticle complex; 
 (d2) removing free detection label that is not bound in the label-analyte-nanoparticle complex from the sample concentrate; and, 
 (d3) detecting the detection label remaining in the sample concentrate that is bound in the label-analyte-nanoparticle complex. 
 
     
     
       3. The method of  claim 2 , wherein the detection label comprises a label selected from the group consisting of enzymes, chromogenic substrates, chromophores, radioisotopes, fluorescent molecules, chemiluminescent molecules, phosphorescent molecules, direct visual labels, and combinations thereof. 
     
     
       4. The method of  claim 1 , wherein:
 (i) the magnetic nanoparticles comprise ferromagnetic nanoparticles; 
 (ii) the conductive polymer is selected from the group consisting of polyanilines, polyparaphenylenes, polyparaphenylene vinylenes, polythiophenes, polypyrroles, polyfurans, polyselenophenes, polyisothianapthenes, polyphenylene sulfides, polyacetylenes, polypyridyl vinylenes, conductive carbohydrates, conductive polysaccharides, derivatives thereof, combinations thereof, blends thereof with other polymers, and copolymers of the monomers thereof; and 
 (iii) the binding pair member is selected from the group consisting of antibodies, antibody fragments, antigens, biotin, avidin and derivatives thereof, hormones, hormone receptors, polynucleotides, aptamers, whole cells, and combinations thereof. 
 
     
     
       5. The method of  claim 1 , wherein:
 (i) the magnetic nanoparticles comprise at least one of Fe(II) and Fe(III); 
 (ii) the conductive polymer is selected from the group consisting of polyanilines, polypyrroles, polythiophenes, derivatives thereof, combinations thereof, blends thereof with other polymers, and copolymers of the monomers thereof; and 
 (iii) the binding pair member is selected from the group consisting of antibodies, antibody fragments, antigens, biotin, avidin and derivatives thereof, hormones, hormone receptors, polynucleotides, aptamers, whole cells, and combinations thereof. 
 
     
     
       6. The method of  claim 1 , wherein:
 (i) the magnetic nanoparticles comprise γ-Fe 2 O 3  (maghemite); 
 (ii) the conductive polymer comprises polyaniline; and 
 (iii) the binding pair member comprises an antibody. 
 
     
     
       7. The method of  claim 1 , wherein the particulate composition comprises particles ranging in size from about 10 nm to about 200 nm. 
     
     
       8. The method of  claim 1 , wherein the weight ratio of conductive polymer to magnetic nanoparticles in the particulate composition ranges from about 0.4 to about 0.8. 
     
     
       9. The method of  claim 1 , wherein the binding pair member is selected from the group consisting of an anti- Escherichia coli  O 157 :H7 antibody, an anti- Bacillus anthracis  antibody, and an anti- Bacillus cereus  antibody. 
     
     
       10. The method of  claim 1 , wherein the particulate composition further comprises a label bound to the conductive polymer. 
     
     
       11. The method of  claim 10 , wherein the label is selected from the group consisting of enzymes, chromogenic substrates, chromophores, radioisotopes, fluorescent molecules, chemiluminescent molecules, phosphorescent molecules, direct visual labels, and combinations thereof. 
     
     
       12. The method of  claim 1 , wherein detecting the analyte-nanoparticle complex in step (d) further comprises:
 (d1) removing BEAM nanoparticles that are not bound to an analyte from the sample concentrate; and 
 (d2) conductimetrically detecting the analyte-nanoparticle complex in the sample concentrate. 
 
     
     
       13. The method of  claim 12 , wherein the particulate composition is in the form of a composite with the conductive polymer coating the magnetic nanoparticles and providing a substrate for attachment of the binding pair member bound to the conductive polymer. 
     
     
       14. The method of  claim 1 , wherein the weight ratio of conductive polymer to magnetic nanoparticles in the particulate composition ranges from 0.1 to 0.8. 
     
     
       15. The method of  claim 1 , wherein the weight ratio of conductive polymer to magnetic nanoparticles in the particulate composition ranges from 0.1 to 0.6. 
     
     
       16. The method of  claim 1 , wherein the weight ratio of conductive polymer to magnetic nanoparticles in the particulate composition ranges from 0.6 to 1. 
     
     
       17. The method of  claim 1 , wherein the particulate composition ranges in size from 50 nm to 100 nm. 
     
     
       18. The method of  claim 1 , wherein the particulate composition ranges in size from 10 nm to 90 nm. 
     
     
       19. The method of  claim 1 , wherein the particulate composition is in the form of a composite with the conductive polymer coating the magnetic nanoparticles and providing a substrate for attachment of the binding pair member bound to the conductive polymer.